As we go about our lives, travelling from one place to another, where is one of the only places where we are outdoors (exposed) and stationary? For this nutjob, gas stations are one of few places where he will have multiple targets, all largely exposed for a length of time and all relatively stationary. I think it is as simple as that.
Agree. Add to that using the ATM, walking the dog, going to the mailbox. They want us to be afraid to leave the house. At that point, they'll begin knocking on doors.
The self-service gas station is the urban equivalent to the waterhole on the Veldt.
A good place for a predator to station himself...
This may be way off, but given that a miss at a gas station could prove disastrous, there may be an element of not being able to miss, as it were. Miss the target, hit a gas pump. It would still all look very planned. Of course, that doesn't explain the "Michael's" connection.